1. Field of the Invention
The present invention relates to a drum washing machine.
2. Background of the Related Art
A washing machine removes laundry dirt and stains using chemical decomposition and mechanical impact through washing, rinsing, and dewatering processes. Generally, there are three types of washing machines: a pulsator washing machine, an agitator washing machine, and a drum washing machine.
Among them, the drum washing machine being provided with a drum having a plurality of projections performs a washing process by slowly and horizontally rotating the drum with a detergent, washing water, and a laundry object in it. In this way, in the drum washing machine, the washing process is performed by impact and frictional force being generated as the laundry is raised and dropped by the projections.
In the drum washing machine, a damage rate of a laundry is lowered and the amount of water for a washing process is saved. Accordingly, the drum washing machine with these advantages is being more widely used.
A general structure of a drum washing machine will be briefly described in reference to FIG. 1.
As shown in FIG. 1, a tub 2 is provided inside a cabinet 1 forming an external case. A drum 3 is rotatably formed on a central part inside the tub 2. A motor 4 is formed on one side of a lower part of the tub 2 and the motor 4 is coupled to a pulley 41 by a shaft. A drum shaft 32 having a drum pulley 31 is formed on a rear part of the drum 3. A belt 5 connects the drum pulley 31 and the motor pulley 41 to each other.
A door 6 is formed on the front part of the cabinet 1 and a gasket 7 is formed between the door 6 and the tub 2.
Also, a hanging spring 9 supporting the tub 2 is formed between two sides of the inner side of an upper face of the cabinet 1 and an upper part of an outer circumferential face of the tub 2.
A damper 8 is formed between two edges of a lower face of the cabinet 1 and two sides of a lower part of the outer circumferential face of the tub 2. The damper 8 absorbs and attenuates vibrations of the tub 2, generated as the drum 3 rotates in a dewatering process.
As shown in FIG. 2, a lower end of the damper 8 is fixed between brackets 12 on a base face 11 of the cabinet 1 by fastenings such as bolts 13 and nuts 14.
In the meantime, the most common problem of the drum washing machine is transient vibration of the drum 3. When the drum 3 is rotated with increasing speed as a dewatering process starts, the transient vibration are generated because of an uneven distribution of laundry load. The damper 8 may be designed bigger to reduce the transient vibration, but in that case, the vibration problem is caused during rated revolution instead.
On the contrary, if the damper is designed to be smaller, the vibration becomes smooth during the rated revolution for dewatering but the transient vibration problem is raised.
The transient vibration generates unpleasant noise and a disorder of component parts and thus, may reduce the lifetime of the washing machine.